Conventional optical networks generally include switch devices that provide a connection between an input port and an output port to establish a channel between first and second optical links. Such switches typically convert the optical signals to electrical signals to make the input/output connections. The switch examines the data stream at a bit level to perform network management and performance monitoring functions. For example, frame headers can contain source and destination information used to route a constant bit-rate data stream in the network. Performance monitoring can include examining selected overhead data to detect and isolate errors within the network.
However, switches that convert data from the optical domain to the electrical domain and back to the optical domain can create an impediment to achieving the bandwidths that developing optical networking technologies potentially offer. For example, dense wave division multiplexing (DWDM) systems multiplex a series of optical signals having varying wavelengths into a single optical fiber. A fiber has a plurality of parallel channels each associated with a particular wavelength. The channel wavelengths have a predetermined spacing to minimize certain effects, e.g., cross talk, and to maximize the number of channels that a fiber can carry.
A switch interfaces with input ports and output ports to provide desired signal paths between selected input and output ports of two DWDM systems. The switch typically provides network management, signal restoration, provisioning, grooming and some level of signal monitoring.
Transparent optical switches refer to switches that do not convert optical signals to electrical signals. An exemplary switch is shown and described in U.S. Pat. No. 5,937,117, to Ishida et al., which is incorporated herein by reference. One disadvantage associated with known transparent optical switches is the limited ability to examine and extract necessary information carried within the optical signal. Thus, adequate network management, performance monitoring, and control within the optical network is relatively complex, costly, and unreliable.
It would, therefore, be desirable to provide a transparent optical switch having enhanced performance monitoring, network management and control functionality.